As strong as an insect’s shell
As strong as an insect’s shell
Wyss research takes cue from nature to create tough, low-cost material
Postdoctoral fellow Javier Fernandez (right) and Don Ingber, director at the Wyss Institute, have created a new material made from discarded shrimp shells and proteins derived from silk called “shrilk.” It is thin, clear, flexible, and hard as aluminum at half the weight. Shrilk not only will degrade in a landfill, but its basic components are used as fertilizer, and so will enrich the soil./ Jon Chase/Harvard Staff Photographer
Harvard researchers at the Wyss Institute for Biologically Inspired Engineering have come up with a tough, low-cost, biodegradable material inspired by insects’ hard outer shells. The material’s inventors say it has a host of possible applications and someday could provide a more environmentally friendly alternative to plastic.
The material, made from discarded shrimp shells and proteins derived from silk, is called “shrilk.” It is thin, clear, flexible, and strong as aluminum at half the weight, according to postdoctoral fellow Javier Fernandez, who began work on chitin-based material as a doctoral student at the University of Barcelona and developed shrilk during a year-and-a-half stint working at the Wyss Institute with Director Donald Ingber.
Ingber, the Judah Folkman Professor of Vascular Biology at Harvard Medical School and Harvard-affiliated Children’s Hospital and professor of bioengineering at the Harvard School of Engineering and Applied Sciences, said companies have already expressed interest in the material, particularly for medical applications. Possible medical uses are boosted by the fact that the ingredients in shrilk have already been approved by the Food and Drug Administration. Potential uses include sutures that would dissolve over time in hernia repair, protective coverings for burns and wounds, and a scaffold on which cells can grow to regenerate tissue.
A major benefit of the material, which was described in a December issue of the journal Advanced Materials, is its biodegradability, Ingber and Fernandez said. Plastic’s toughness and moldability represented a revolution in materials science during the 1950s and ’60s. Decades later, however, plastic’s very durability is raising questions about how appropriate it is for one-time applications such as plastic bags, or short life-span consumer goods, used in the home for a few years and then tossed into a landfill where they will decompose for centuries.
“All this plastic, what’s the point of making something that lasts 1,000 years?” Fernandez asked.
Shrilk not only will degrade in a landfill, but its basic components are used as fertilizer, and so will enrich the soil.
Natural materials, Fernandez said, were supplanted by synthetic materials partly because synthetics can be easily controlled in manufacturing and made into a wide variety of goods. Natural materials are making a comeback, however, as scientists learn from nature the manufacturing techniques needed to mimic the properties that make them desirable. Shrilk is a good example of the Wyss Institute’s mission, which is to learn how to make things from nature’s own engineering.
“This is the second chance for natural materials,” Fernandez said.
Shrilk’s secret, Fernandez and Ingber said, is not just its chemistry but also its design. There are two basic ingredients, a variation on the material chitin that makes up a large part of an insect’s tough outer layer, called chitosan, and fibroin, a protein derived from silk. But just combining those two ingredients doesn’t produce a hard, flexible material. Instead of blindly combining the materials, Fernandez and Ingber looked to nature to see not just what materials were used, but how.
In an insect’s body, the fibroin protein and chitin are layered, creating the kind of stiff design that gives plywood its strength and rigidity. By mimicking nature’s design and layering the chitosan and fibroin protein, shrilk was born.
“Much of the structural properties found in nature are not just chemistry, they’re architecture,” Ingber said.
Shrilk has great potential, the two said. Chitin is one of the most abundant materials in nature, found in everything from shrimp shells to insect bodies, snail and clam shells. That makes shrilk not only low cost, but also potentially scalable should it be used in applications demanding a lot of material.
Work on shrilk is continuing in the lab, the two said. Ingber said the material becomes flexible when wet, so they’re exploring ways to use it in moist environments. They’re also developing simpler manufacturing processes, which could be used for products in non-medical applications, like for computer cases and other products inside the home. They’re even exploring combining it with other materials, like carbon fibers, to give it new properties.
About Harvard Medical School (HMS)
Driving Change. Building Momentum. Making History.
“Since 1872, Harvard Medical School has been the incubator of bold ideas—a place where extraordinary people advance education, science and health care with unrelenting passion.
Whether training tomorrow’s doctors and scientists, decoding the fundamental nature of life, advancing patient care or improving health delivery systems around the world, we are never at rest. Allied with some of the world’s best hospitals, research institutes and a University synonymous with excellence, the School’s mission remains as ambitious as it is honorable: to alleviate human suffering caused by disease.”
### About Harvard School of Public Health (HSPH)
Harvard School of Public Health is dedicated to advancing the public’s health through learning, discovery and communication. More than 400 faculty members are engaged in teaching and training the 1,000-plus student body in a broad spectrum of disciplines crucial to the health and well being of individuals and populations around the world. Programs and projects range from the molecular biology of AIDS vaccines to the epidemiology of cancer; from risk analysis to violence prevention; from maternal and children’s health to quality of care measurement; from health care management to international health and human rights.
### About Harvard University.
Established in 1636, Harvard is the oldest institution of higher education in the United States. The University, which is based in Cambridge and Boston, Massachusetts, has an enrollment of over 20,000 degree candidates, including undergraduate, graduate, and professional students. Harvard has more than 360,000 alumni around the world.
Harvard University is devoted to excellence in teaching, learning, and research, and to developing leaders in many disciplines who make a difference globally. Harvard faculty are engaged with teaching and research to push the boundaries of human knowledge. For students who are excited to investigate the biggest issues of the 21st century, Harvard offers an unparalleled student experience and a generous financial aid program, with over $160 million awarded to more than 60% of our undergraduate students. The University has twelve degree-granting Schools in addition to the Radcliffe Institute for Advanced Study, offering a truly global education.
‘Universities nurture the hopes of the world: in solving challenges that cross borders; in unlocking and harnessing new knowledge; in building cultural and political understanding; and in modeling environments that promote dialogue and debate… The ideal and breadth of liberal education that embraces the humanities and arts as well as the social and natural sciences is at the core of Harvard’s philosophy. ’/ Drew Gilpin Faust
### * The above story is adapted from materials provided by Harvard University